Field of the Invention
The invention relates to a method for safe access of at least one mobile control unit to at least one field device.
Description of Related Art
It is common in modern process automation to monitor processes or media using measurements with measuring devices or to influence them using control elements. Such field devices—i.e., measuring devices or sensors and control elements or actuators—are usually connected to control rooms via so-called fieldbuses.
In order to directly contact the field devices on site, the field devices have, in some instances, so-called control and display units for representation of information as well as input or selection of data. Alternatively, there are particular interfaces, which allow direct connection of a, in particular mobile, control unit to the field device. These are called, for example, service interfaces. Some field devices also have wireless interfaces, which, in some instances, are a fixed component of the field device or are inserted in the field device via an adapter.
So-called handhelds are used for access to the field devices. These are generally specially developed to be able to be used in industrial applications and, in particular, for process automation.
These mobile—i.e., for the most part, portable—handhelds allow, in some instances, a direct connection to a field device or they can be connected to the respective fieldbus for influencing the field device or, for example, for reading data.
A mobile operating unit in the following is any type of portable or transportable unit that allows an input of data or information, a selection between alternatives, a display of data or processes, or another type of implementation of human-machine interaction—here, in particular with a field device.
Insofar as it is possible to directly access a field device, it is necessary to prevent non-authorized access from taking place.
Since processes are controlled and monitored using field devices, this function, on the one hand, needs to be ensured and, on the other hand, valuable information can be obtained from the processes. Thus, on the one hand, it is necessary to prevent interference of control of the processes or, respectively, their measurements, e.g., by setting of incorrect parameters or changing of software. On the other hand, data that may, for example, provide information about formulas etc. should not reach unauthorized persons.